The project is a prospective, interdisciplinary, longitudinal study of senile dementia of the Alzheimer type (SDAT). The aim is the correlation of clinical and autopsy findings. The diagnosis will be established on clinical grounds after eliminating other possible causes. Extensive physical, neurologic, radiologic, neuropsychologic, and language testing will be completed at the first encounter with subsequent updating of these data at regular, usually six-month, intervals. Suitable control population will be selectively studied for comparison. Autopsy material derived from this group will have neuropathologic, immunohistochemical studies for hormones and peptides, neurotransmitter, and quantitative neuron examinations. This longitudinal study during life with subsequent autopsy study will provide information regarding the taxonomy of the disease, subgroups, clinical course, relationship of various behavioral or language disorders with regional or system involvement, compensation and decompensation mechanisms in the nervous system, and survival predictions.